Theme customization page

[Ullaakut]

Depends on issues #76 & #67 & #78

• Allow the user to choose between preset themes
• When the user chooses a theme, send a request to the backend to update the theme
• Provide a button to the grid customization page (which will come later on)

Theme customization

• Allow the user to change the main background color
• Allow the user to change the sidebar background image
• Allow the user to change the fonts (choosing between preset fonts)
• Allow the user to change the font colors

API

• When the user is uploading images for his theme, use the backend route to upload them
• The backend will give you the path to the image that has been uploaded
• Using this path, the colors and fonts that the user chose, generate a css file using Javascript
• Upload this css file using the backend route from Theme backend route #76